Method of sulfurizing terpenes



July 27, 1948. R. w. WATSON METHOD 0F SULFURIZING TERPENES Filed April26, 1946 wam.

mwwokm ow m Naz ll f QW ww .WOQQEW MMQQmK lum. Lmxu mtoob u t ,Q S35 mwmm, E UG okovm 9m w X f NN xx wm mm of I/ YQ km i f mo o vm mw Q 3.35m

Patented July 27, 1948 METHOD F SULFURIZING TERP'ENEB Roger W. Watson,Chicago, Iii., signor to Standard Oil Company, Chicago. Ill., acorporation of Indiana Application April 28, 1948, Serial No. 665,291

ilClaims. 1

The present invention relates to an improved method of sulfurizingterpenes with elemental sulfur.

Terpenes have heretofore been sulfurized with elemental sulfur by mixingthe terpene and the sulfur and heating the mixture to the desiredreaction temperature. Another method commonly employed is to heat theterpene to the reaction temperature while adding thereto small amountsof the sulfur until the required amount of sulfur has been added. Thesemethods of sulfurizing terpenes have the disadvantage in that it isextremely difficult, if not impossible, to regulate the temperature orto control the rate of reaction due'to the exothermlc nature of thereaction. The incremental or continuous addition of sulfur to thereaction involves many didiculties since the light hydrocarbons refluxat the reaction temperature and the condensate impedes the addition ofdry sulfur. Because of difficulties encountered in controlling theexothermic reaction when terpenes are sulfurized in the mannerdescribed, the sulfurized terpenes are very dark in color.

It is an object of the present invention to provide a method ofsulfurizlng terpenes in which the exothermic reaction can be controlled.Another object of the invention is to provide a method of sulfurizingterpenes which avoids excessive polymerization and color formation.Another object of the invention is to provide a method of sulfurizingterpenes which results in improved yields. Other objects and advantagesof the present invention will become apparent from the followingdescription thereof read in conjunction with the accompanying drawing,which is a flow diagram of a preferred method of carrying out thepresent invention.

I have discovered that the foregoing objects can be attained by a methodof sulfurizatlon in which the terpene is added in the liquid phase to abody of molten sulfur maintained at a certain optimum temperature.Terpenes which can be sulfurized by the herein-described method,including the monocyclic, blcyclic and acyclic terpenes, as well aspolyterpenes. Examples of species falling within these classes ofterpenes are pine oil, turpentine, cymene, alpha-pinche, beta-pinche,allo-oclmene, fenchenes, bornylenes, menthadienes such as limonene,dipentene, terpinene, terpinolenes and Afil-p-menthadiene,sesquiterpenes, diterpene, and polyterpenes having the general formula(CsHaln, Mixtures of such terpenes can also be employed in theinvention. In accordance with the present invention,

elemental sulfur is stirred at a temperature above its melting point,for example at a temperature of from about 325 F. to about 400 F.. andpreferably at a temperature of from about 350 F. to about 375 F., andthe terpene slowly added in the liquid phase to the molten sulfur. Tofacilitate adequate stirring, it is advantageous to add a Smau amount orthe terrene. preferably when the molten sulfur has reached a temperatureof about 310 F.340 F., and the temperature then raised to the desiredreaction temperature, for example 375 F. before the remaining portion ofthe terpene is added. Usually, the addition of about 5% of the terpenewill be found adequate to facilitate adequate stirring; the remaining ofthe terpene being then added at the desired reaction temperature.

The sulfurized terpenes contain some active sulfur, as evidenced by thedarkening of a copper strip submerged in about 0.5% solution of thesulfurized terpenes in a hydrocarbon oil maintained at a temperature ofabout 210 F. For certain uses such as lubricating oil additives, thepresence of such active sulfur compounds in the sulfurized terpenes isundesirable'. These socalled active sulfur compounds can be deactivatedby treating the same with an alkali metal sulfide, such as sodiumsulfide or with a mixture of an alkali metal sulfide and a small amountof an alkaline material such as for example sodium hydroxide.

After the sulfurization reaction is completed. which will take fromabout 5 minutes to about 60 minutes or more, and usually about 15minutes, the sulfurized terpene is rendered non-corrosive bydeactivation by the addition of an alkali metal sulfide, such as sodiumsulfide, preferably added as an 18% aqueous solution. It will beunderstood that the time of sulfurization is dependent largely upon therate of refiuxing and other coollng means for controlling the exothermlcreaction. During the deactivation stage the reaction mixture ismaintained at a temperature from about 200 F. to about 260 F'., andpreferably at about 230 F. It is desirable during the deactivation stageto maintain the reaction mixture under a pressure suilcient to retainthe light ends of the product, usually a pressure of about 'I poundswill be found to be sufficient for this purpose. While it is desirableto carry out the deactivation at a preferred temperature at about 230 F.and a pressure of about 7 pounds, higher or lower temperatures andpressures may be employed. After the sulfurized terpene reaction productis deactivated, such as by treatment with the sodium sulfide, thereaction mass is permitted to separate into an upper layer comprisingthe sulfuriaed terpenes and a lower layer comprising sodium polysulfidesolution. After the sodium polysuliide solution layer is separated fromthe sulfurized terpene product the latter is washed at a temperature offrom 'about 200 F. to about 250 F., and preferably at about 220 F. witha sodium chloride solution. The brine solution is then settled and drawnoil. The washed deactivated sulfurized terpene product is then filteredand again washed with a 20% sodium chloride solution to remove the lasttraces of alkali metal polysulflde from the sulfurized product. Ifdesired, the sulfuri'zed terpene product can then be fiash distilled,preferably under reduced pressure, to remove any unreacted hydrocarbonsor slightly sulfurized lighter boiling terpenes. preferably using aninert gas, such as nitrogen for stripping. In order to avoid thedarkening of the sulfurized terpene product, it is essential that thematerial be held at a temperature of from about 250 F. to about 350 F.,and preferably at about 300 F. for a period of time no longer than aboutto 35 minutes.

The following description of sulfurizing dipentene according to thepresent invention to obtain a product suitable for use as a lubricantadditive is given by way of example only and not intended as limitingthe scope of the invention.

Referring to the accompanying drawing. sulfur forming about by weight ofthe sulfurization reaction mixture from sulfur storage tank il isintroduced through a line ii to the iaclreted reactor I2 provided withheating means, such as superheated steam introduced through a line i8,and temperature control means I4. If desired, reactor I2 may be providedwith a Dowtherm boiler to supply the necessary heating. The .iacketedreactor I2 is also provided with cooling means such as for example waterinlet and outlet Il and Il, respectively. After the sulfur is added tothe reactor i2, it is heated to a temperature of about 325 F. to 330 F.at which time about 5% of the required amount of dipentene from storagetank i1 is introduced in the liquid phase into the reactor l2 throughpump Il and lines il and 2l. and the mixture stirred by means of stirrer2| or other suitable means. The temperature of the reactor contents isthen increased to a temperature of about 375 F. and the balance of theliquid dipentene introduced into the reactor as rapidly as possible. Thequantity of dipentene employed amounts to about by weight of thesulfur-dipentene reaction mixture. During this period the temperaturewithin the reactor is maintained at approximately 375 F. suitably bymeans of a reflux condenser 22. The hydros'w sulde formed is vented fromthe reactor i2 through condenser tube 23.

After the completion of the sulfurization re action,A the temperature inthe reactor i2 is lowered to about 230 F. by introducing water throughline Il into reactor Jacket I2a.

The sulfurized dipentene is then deactivated by treatment with an 18%aqueous solution of sodium sulfide from tank 24 introduced into thereactor i2 via pump 2l and line 20. From about 10% to 20%, andpreferably 14% to 15% by weight of sodium sulfide is usually suiiicientto deactivate the suifurized dipentene product. During the time thesulfurized dipentene reaction product is being deactivated with thesodium sulfide. a temperature of about 230 F. is maintained in thereactor by. passing steam into the Iiacket ila. The mixture ofsulfurized dipentene reaction products and sodium sulfide is stirred atthe proper temperature for a period of about two hours while maintaininga pressure of about 'I pounds upon the reactor to retain the light ends.At the end of the two hour deactivation period, the reaction maas inreactor i2 is permitted to stratify into an upper layer, comprising thedeactivated sulurized dipentene product. and a lower layer of sodiumpolysulfide solution. and the latter drawn off through lines 20 and 21to a sodium polysuifide storage tank 2l.

After the sodium polysuliide solution is withdrawn from the Lreactor i2.the deactivated suliurized dipentene is washed with a 20% sodiumchloride solution introduced into the reactor i2 from tank 2l throughpump 30 and lines IlV and 2B. The washed deactivated sulfurizeddipentene is then settled and the sodium chloride drawn oi'f throughlines 20 and 32 to the sewer.

The solid sodium polysulflde remaining in the Washed deactivateddipentene, together with any other solid or colloidal impurities. areremoved by introducing the sulfurized dipentene via lines 2l and Il andpump 34 to a suitable filter 3B, which may be a Sparkler type filter.Filter Il is maintained by suitable means at a temperature of about 320F. and operated at a pressure of about 20 pounds per square inch. It hasbeen found that a filter rate of 121/2 gallons per hour per square footis suitable. Lower or higher pressures or temperatures can of course beemployed. but with some sacrifice in emciency.

The filtrate from the nlter 3| is passed via line 38 to a wash drum l1,provided with stirrinU means 3l wherein the filtered sulfurizeddipentene is washed one or more times with a 20% sodium chloridesolution from tank 20 via pump Il and lines 3| and Il to remove the lasttraces of sodium polysulfide. The sodium chloride solution in wash tank31 is withdrawn via line 4l to tank 40a. The used sodium chloridesolution may be dumped to the sewer. or if a plurality of washes areused. the last wash may be recycled to the wash drum for the washing ofthe next batch The washed filtered sulfurized dipentene from wash tankIl is passed via'pump 4I and lines 42 and 43 to a preheater 44 in whichthe sulfurized dipentene is heated to a temperature of about 300 F. andthen introduced into a stripping tower 45, wherein the heated suifm'izeddipentene is .flash distilled at about 50 mm. pressure and withsufficient nitrogen purge gas. introduced from nitrogen supply tank 4lvia line 41 to reduce the sulfurized dipentene product to a bottomsfraction having the desired sulfur content. If desired, a portion of thenitrogen from tank 4l may be introduced via lines 41 and 48 to line 43and introduced into the stripping tower 4l together with the sulfurizeddipentene. The stripping tower H5 may be provided with heating and/orcooling coils 48.

The amount of nitrogen used is that necessary for maintaining agitationwithin the stripper 4l.

pump Il, passed through a cooler exchanger I1 and through line Il tostorage tank Il.

The filtered sulfurized dipentene after the sodium chloride wash may beused as such; however, for use as a lubricant additive, it is desirableto remove the light ends of the product and concentrate the bottoms to asulfur content of from about 30% to about 50%. and preferably about 40%.Sulfurized terpenes, particularly sulfurized dipentene having a sulfurcontent within this range. are suitably employed as lubricant additivesto inhibit corrosion, particularly corrosion of alloy bearings and asextreme pressure agents.

Depending upon the intended use of the sulfurized terpene. any amount ofsulfur can be employed in the sulfurization of the terpene by theherein-described method. However, for the preparation of sulfurizedterpenes as a lubricant additive, the sulfur-terpene reaction mixtureshould contain from about 25% to about 50%, and preferably about 40% byweight of sulfur, and from about 50% to about 75%, and preferably about60% by weight of the terpene.

The improvement obtained by sulfurizing terpenes in the mannerherein-described is illustrated by the data in the following table inwhich color and sulfur content comparisons are made between terpenessulfurized in accordance with the present invention, indicated as methodA, and terpenes suifurized by heating a mixture of sulfur and terpene,indicated as method B.

l Determined by the method described in Industrial and EngineerinvyChemistry, vnl. i8, 11.1040920).

The above data demonstrate the improvement in color and increase insulfur content of deactivated suifurized terpenes obtained in changingfrom the usual method of sulfurizing terpenes to the sulfurizationmethod in accordance with the present invention. The color improvementin the method of the present invention is about 30%. The increase insulfur in the deactivated sulfurized terpene is an improvement whichreflects directly in cost of production. In addition to theseadvantages, the important advantage of the hereindescribed method is inthe simplicity of operation. Other advantages are that the heat taken upby the incoming terpene. such as dipentene, helps to control the speedof the reaction; further, the dipentene reacts almost instantly with'the sulfur so that substantially no polymerization or resinificationtakes place. This results in improved color and yields.

While I have described in detail a preferred embodiment of my invention,it should be understood that the invention is not limited to any of thedetails hereinabove set forth, except as defined by the appended claims.

I claim:

1. The method of sulfurizing terpenes comprising heating sulfur to atemperature above its melting point, but not above about 400 F.,introducing liquid terpene in said molten sulfur and maintaining saidtemperature for a time sum- 6 cient to substantially complete thesulfurization of said terpene.

2. The method of sulfurizing a terpene comprising heating sulfur to atemperature of from about 325 F. to about 400 F., introducing a terpenein the liquid phase into said molten sulfur and maintaining the reactionmixture at a temperature within the range of about 325 F. to about 400F. for a time sufficient to complete the sulfurization of said terpene.

3. The method of sulfurizing a terpene comprising heating sulfur to atemperature of 310 F. to 340 F., introducing a small amount of theterpene into said heated sulfur, increasing the temperature ofythesulfur-terpene mixture to a temperature of about 350 F. to 375 F.,introducing the remainder of the terpene in the liquid phase into thesulfur-terpene mixture and maintaining the reaction mixture at atemperature of about 350 F. to about 375 F. for a time sumcient tosubstantially complete the sulfurization of said terpene.

4. 'I'he method of surfurizing a terpene as described in claim 3 inwhich the terpene is a menthadiene.

5. The method of sulfurizing a terpene as described in claim 3 in whichthe terpene is dipentene.

8. The method of sulfurizing a terpene comprising heating sulfur to atemperature of about 350 F. to about 375 F., introducing a terpene inthe liquid phase into said molten sulfur, maintaining the reactionmixture at a temperature of about 350 F. to about 375 F., for a timeaufficient to substantially complete the sulfurization of said terpene,treating said sulfur-ized terpene with an alkali metal sulfide,separating the alkali metal sulde from the sulfurized terpene productand washing the sulfurized terpene product with a sodium chloridesolution.

7. The method of sulfurizing a terpene comprising heating sulfur to atemperature of about 350 F. to about 375 F., introducing a terpene inthe liquid phase into said molten sulfur, maintaining the reactionmixture at a temperature of about 350 F. to about 375 F. for a timesufficient to substantially complete the sulfurization of said terpene,treating said sulfurized terpene with an alkali metal sulfide,separating the alkali metal sulfide from the sulfurlzed terpene product,washing the sulfurized terpene product with a sodium chloride solutionand distilling the washed sulfurized terpene product in the presence ofan inert gas to remove unreacted hydrocarbons and low boiling sulfurizedterpenes.

8. The method of preparing a sulfurized terpene lubricant additivecomprising heating elemental sulfur to a temperature of 310 F.-340 F.,adding a small amount of terpenes to the heated sulfur, heating theterpene-sulfur mixture to a temperature of about 350 F. to about 375 F.,adding the remaining portion of the terpene to the heated mixture,maintaining the reaction mixture at a temperature of about 350 F. toabout 375 F. for a time sufficient to substantially complete thesulfurization of the terpene, reducing the temperature of the sulfurizedterpene reaction mixture to a temperature of from about 200 F. to about250 F., adding an alkali metal sulfide to the sulfurized terpenereaction mixture to remove corrosive sulfur therefrom, separating thealkali metal sulfide from the sulfurized terpene reaction product,washing the sulfurized terpene reaction product with a sodium chloridesolution and distilling the washed suiiurized terpene reaction productin the presence of an inert gas at a temperature of from about 250 F. toabout 350 F. to obtain a bottoms fraction containing from about 30% toabout 50% sulfur.

9. The method of preparing a suliurized dipentene lubricant additivecomprising heating elemental 4sulfur to a temperature ot about 325 F. toabout 330 F., adding about 5% of the required di'pentene in the liquidphase to said heated sulfur,- heating said sulfur-dipentene mixture to atemperature of about 375 F., adding the remaining portion of therequired dipentene in the liquid "phase to said heated dipentene-suli'urmixture, maintaining the raction mixture at a temperature of about 375F. for a time sumcient to substantially complete the sulfurization o!said dipentcne, lowering the temperature of the reaction mixture toabout 230 F., adding a sodium sulfide solution to the reaction mixtureto deactivate the corrosive sulfur compounds in 8 said suliurizeddipeutene product, separating the sodium sulfide solution trom thesulfurized dipentene reaction product, washing .the deactivatedsulfurized dipentene product with a 20% sodium chloride solution,filtering the washed sulfurized dipentene product and distiiling thefiltrate at a temperature of about 300 F. in the presence of nitrogen toobtain a bottoms fraction containing about 40% sulfur.

ROGER W. WATSON.

REFERENCES CITED The following references are oi record in the nie ofthis patent:

UNITED STATES PATENTS Number Name Date 480,235 Dubbs Aug. 2, 18921,884,762 Lloyd et al. Oct. 25, 1932 2,156,919 Merriam May 2, 19392,222,482 Hagge Nov. 19. 1940 2,332,165 Ott Oct. 19, 1943

